In a number of different surgical operations, the objective is to locate, break apart and remove unwanted tissue from the body. For example, one of the more common aliments associated with the eye is the formation and presence of cataracts in the eye. As is known, a cataract is a cloudy area in the eye's lens that can cause vision problems. The lens is the part of the eye that helps focus light onto the retina. The lens is made mostly of water and protein. The protein is arranged to let light pass through and focus on the retina. Sometimes some of the protein clumps together and starts to cloud a small area of the lens. This is a cataract. The most common type of cataract is related to aging.
There are a number of different surgical techniques for breaking apart and removing a cataract from the eye and as a result, there are a number of different surgical instruments that can be used to accomplish this task. However, each of these surgical instruments, either alone or in combination with other instruments, is constructed to accomplish the same objective, namely breaking apart the cataract and then removing the tissue from the eye.
Small incision cataract surgery is today one of the more prevalent operations for removing a cataract from the eye and in particular, the small incision cataract surgery is most commonly performed by ultrasound phacoemulsification. With reference to FIGS. 1-3, a coaxial surgical instrument 20 defined by an ultrasonic probe 30 with coaxial infusion provided by a sleeve 40 of the probe 30 is typically inserted through a wound or incision 10 made in the cornea, limbus or sclera of the eye. The incision 10 is usually between about 2.2 mm to 3.5 mm but it may be slightly smaller or larger depending on the particular application and patient. The infusion maintains the anterior chamber while the lens nucleus is emulsified due to longitudinal ultrasonic vibrations provided at the working tip of the probe 30. The infusion (treatment fluid) baths the tissue in the region adjacent a working tip 32 and the probe 30 includes means adjacent the working tip 32 for withdrawing the suspension of particles of the tissue in the fluid (infusion) resulting from the ultrasonic vibration of the working tip 32. This type of instrument 20 is described in more detail in U.S. Pat. No. 3,589,363, which is hereby incorporated by reference in its entirety. Following emulsification and aspiration of the nucleus, the softer cortex of the lens can be removed by a different co-axial instrument through the same incision. This other co-axial instrument usually has a smaller diameter than the ultrasonic probe 30. Alternatively, the softer cortex can be removed in a bimanual fashion through two paracentesis incisions in the cornea or limbus of the eye, which are separate incisions than the emulsification incision and much smaller in length, e.g., usually 1 mm or less.
More recently, another type of emulsification has become popular. More specifically, bimanual ultrasound emulsification has become popular in which the infusion (treatment fluid) and emulsification are divorced and delivered through two separate incisions which can each range in length between about 1 mm and 2.5 mm. The advantage of the bimanual approach is that the final incision size is smaller than the size of the single incision that is used in the above co-axial approach. This leads to quicker healing of the incision (wound) and quicker rehabilitation of the patient.
Energy sources other than ultrasound have been used to emulsify the lens in both the coaxial and manual approaches. For example, the energy source of the probe can be laser energy as described in greater detail in U.S. Pat. Nos. 5,324,282 and 5,906,611, both of which are hereby incorporated by reference in their entireties and which the present applicant is a named inventor. Other energy sources, such as water or water jets can be used to emulsify or break up the lens.
In all approaches, whether coaxial or bimanual, the cannulas that define the surgical instrument, such as instrument 20, are usually round and are inserted through a slit incision or wound 10. This creates a situation where it is not possible to obtain a closed system since edges 12 of the incision 10 separate due to the presence of the cannulas 30, 40, thereby creating two pockets or openings 11 at the ends of the incision 10 where the cannulas 30, 40 are not present as shown in FIG. 3. As a result, fluid leakage occurs on either side of the cannulas, i.e., the two end pockets or openings 11. A true closed system is advisable so that no wound leakage occurs. This would provide the surgeon with a more stable anterior chamber leading to greater intraoperative control in which the anterior chamber would not fluctuate between deep and shallow, which can lead to damage of intraocular structures within the eye during emulsification, including the cornea, iris, and posterior lens capsule of the eye.